Police Maj. Richard Riddle said investigators believe the shootings happened Tuesday night just before the restaurant's 11 p.m. closing time. A relative called police about 1 a.m. Wednesday after becoming concerned about them not returning home and finding the two slain men.
Riddle said the attackers killed the workers for no apparent reason.
"These individuals were hell bent on robbery," Riddle said. "They came in guns up, guns pointed, going directly behind the counter — a takeover style robbery."
He said investigators were trying to determine what was stolen.
The workers, ages 34 and 36, died at the scene, Riddle said. Authorities didn't immediately release their names.
Restaurant co-owner Ameer Saadeh called the shootings "unbelievable."
"All we can do is pray for them," he told The Indianapolis Star. "That's all. God was watching what happened."
Riddle asked for the public's help in identifying the attackers, saying it's urgent that they're captured quickly.
"Our fear is if we don't get these individuals into custody, that further violence may occur," he said. "They've clearly shown they aren't afraid to take the lives of two innocent people."